Cell culture has been utilized for many years in life science research in an effort to better understand and manipulate the cellular component of living systems. Cells are typically grown in a static environment, on petri dishes or flasks, in which each experiment uses a stream of sterile, disposable products. These cell culture methods are very labor-intensive especially when a large number of studies need to be performed.
Traditional cell culture systems depend on controlled environments for cell maintenance, growth, expansion, and testing. Typical cell culture laboratories include laminar flow hoods, water-jacketed incubators, controlled access by gowned personnel, and periodic sterilization procedures to decontaminate laboratory surfaces. Personnel require extensive training in sterile techniques to avoid contamination of containers and cell transfer devices through contact with non-sterile materials. Despite these measures, outbreaks of contamination in traditional cell culture laboratories, e.g., fungus or bacterial contamination, commonly occur, often with the impact of compromising weeks of research and halting operations for days or weeks.
Trained technicians under a sterile, laminar flow hood typically perform cell culture. Cells are grown in flasks or bioreactors and maintained in incubators that provide the requisite thermal and gas environment. Cultures are removed from incubators and transported to a sterile hood for processing. Cells can be harmed when removed from their thermal and gas environment. The frequent transport and manipulation of the culture represents an opportunity for contamination from a single bacterium that can cause weeks of work to be wasted. The nutrient cell culture medium includes a color indicator that is visually inspected by the technician on a daily basis, at a minimum. When the color is deemed to indicate that the pH is deviating from a healthy range, the cells are removed from the incubator, the old media is manually removed and fresh media is injected. This process is adequate at best.
Perfusion systems provide a three-dimensional cell culture environment that reproduces critical aspects of the dynamic in vivo environment. In vitro perfusion systems allow tissue-engineered cells to develop and organize as if inside the body. Biotechnology companies, universities, and research institutes are attempting to develop complex tissue replacements including liver, pancreas, and blood vessels, among others. These complex tissue products require advanced biochamber perfusion systems that are capable of mimicking in vivo development dependent stimulation for optimal tissue development. A perfusion cell culture system's primary purpose is to provide a pump that will continuously re-circulate medium. Standard experiment manipulations, such as media replacement (when it is no longer at the proper pH), cell and media sampling, and fluid injections, are traditionally performed by a laboratory technician in a sterile hood. In an age where genetically engineered products will be FDA approved and drug compound costs are hundreds of millions of dollars, the traditional way of performing cell culture is no longer acceptable.
One critical issue to be addressed in any cell culture application involves precision reproducibility and the elimination of site-to-site and batch-to-batch differences so that cell products and experiments will be consistent in different biochambers or different physical locations. This is particularly difficult to accomplish when culture viability is determined solely on subjective visual cues, i.e., medium color and visualization under a microscope.
In a purely manual environment, quality control is accomplished by selecting qualified personnel, providing them with extensive training, and developing a system of standard operating procedures and documentation. In an automated environment, the principles of process validation are used to demonstrate that the process is precise, reliably consistent, and capable of meeting specifications. The principles of statistical process control are then implemented to monitor the process to assure consistent conformance to specifications.
The particular physical and biological requirements for the growth and modification of cells and tissues of interest vary. However, two key components are necessary for cell and/or tissue culture: cells that are capable of replicating and potentially differentiating and an in vitro system containing biocompatible materials that provide for the physiological requirements for the cells to remain viable, proliferate, differentiate, and/or organize into desired tissue structures. These requirements include temperture, pH, surfaces appropriate for cell attachment, nutrient exchange, waste removal, and oxygenation. These systems should be automated and amenable for routine use by the thousands of research laboratories, universities, tissue engineering companies, hospitals, and clinics that perform research requiring consistent and reliable results and also those that serve patients intended to benefit from transplantation cells and tissues in native or genetically altered form without adversely affecting product quality and, particularly, product sterility.
Cell and organ transplantation therapy to date has typically relied on the clinical facility to handle and process cells or tissues through the use of laboratory products and processes governed to varying degrees by standard operating procedures and with varying regulatory authority involvement. The procedures to date, however, generally have not required extensive manipulation of the cells or tissue beyond providing short term storage or containment, or in some cases, cryopreservation. With the addition of steps that require the actual growth and production of cells or tissues for transplantation, medium replacement, sampling, injections of drug/compound dosing, physiologic and set-point monitoring, and quality assurance data collection, there are many considerations that need to be addressed in order to achieve a reliable and clinically safe process. This issue is the same regardless of whether the cell production is occurring at the patient care location, as might be the case for the production of cells for a stem cell transplant, or at a distant manufacturing site, as might be the case for organ and tissue engineering applications.
Platform-operated culture systems, typically referred to as bioreactors, have been commercially available. Of the different bioreactors used for mammalian cell culture, most have been designed to allow for the production of high density cultures of a single cell type. Typical application of these high density systems is to produce a conditioned medium produced by the cells. This is the case, for example, with hybridoma production of monoclonal antibodies and with packaging cell lines for viral vector production. These applications differ, however, from applications in which the end-product is the harvested tissue or cells themselves. While traditional bioreactors can provide some economies of labor and minimization of the potential for mid-process contamination, the set-up and harvest procedures involve labor requirements and open processing steps, which require laminar flow hood operation (such as manual media sampling to monitor cell growth). Some bioreactors are sold as large benchtop environmental containment chambers to house the various individual components that must be manually assembled and primed. Additionally, many bioreactor designs impede the successful recovery of expanded cells and tissues and also can limit mid-procedure access to cells for purposes of process monitoring. Many require the destruction of the bioreactor during the harvesting process.
It should therefore be appreciated that within tissue engineering companies, cellular therapeutic companies, research institutions, and pharmaceutical discovery companies there is a need for an automated cell and tissue culture system that can maintain and grow selected biological cells and tissues without being subject to many of the foregoing deficiencies. There also is a need for a lower cost, smaller, automated research and development culture system which will improve the quality of research and cell production and provide a more exact model for drug screening.